sdasdas  Rendering of a fountain with fluid pillards

October 18, 2019 / pa

VISUS Publication

by Stefan Reinhardt, Tim Krake, Bernhard Eberhardt, and Daniel Weiskopf

The 12th ACM SIGGRAPH ASIA  takes place in Brisbane, Australia on November 17-20, 2019, one of the world's most important conferences in the field of computer graphics and interactive technology. Alongside the conference SIGGRAPH, SIGGRAPH Asia is the second annual meeting of the ACM Special Interest Group on Computer Graphics and Interactive Techniques.

This year VISUS is also represented by the doctoral program Digital Media and the publication "Consistent Shepard Interpolation for SPH-Based Fluid Animation" (authors: Stefan Reinhardt, Tim Krake, Bernhard Eberhardt, Daniel Weiskopf).

A new technique for correcting discretization errors in Smoothed Particle Hydrodynamics (SPH) based fluid animation is presented. SPH is a Lagrangian technique to simulate fluids and is widely used in the field of computer animation. To simulate the fluid body, the fluid quantities, such as density or pressure, are approximated at given positions. Due to this discretization process, inevitable errors are introduced. The so-called Shepard correction is typically used to reduce this kind of error. This correction scheme, however, employs the density. On the other hand, the density is a fluid quantity itself and undergoes this correction as well. Therefore, the Shepard correction results in an inconsistent scheme.

The authors resolve this issue and present a consistent method to compute the kernel correction. A power method is used to compute the correction factors, resulting in an efficient and unconditionally stable algorithm. In addition, a kernel gradient correction scheme is presented as well as adjustments to a well-known rigid boundary model. The presented method increases the accuracy of the simulation. Moreover, the noise in the density field is significantly reduced, i.e., a smooth density distribution throughout the fluid body is achieved.

Snapshot of the fluid pillar scenario consisting of 60.000 particles simulated with WCSPH. From left to right: simulation without kernel correction, with classical Shepard correction, and with our method. Particles are colored with respect to density. We sliced out the front left quarter of the tower to show the inside of the fluid. With our method, we obtain a significantly smoother density field compared to simulations conducted without kernel correction or with classical Shepard correction.
Snapshot of the fluid pillar scenario consisting of 60.000 particles simulated with WCSPH. From left to right: simulation without kernel correction, with classical Shepard correction, and with our method. Particles are colored with respect to density. We sliced out the front left quarter of the tower to show the inside of the fluid. With our method, we obtain a significantly smoother density field compared to simulations conducted without kernel correction or with classical Shepard correction.
The collapsing fluid block simulated with DFSPH (upper row) and WCSPH (lower row). From left to right: no kernel correction, classical Shepard correction, and our method. For both uncorrected and classical Shepard correction, we observe fine-grained noise in the density field. Using our technique, we achieve a completely smooth density field for WCSPH (lower right). Considering DFSPH, our method still significantly improves the smoothness of the density field.
The collapsing fluid block simulated with DFSPH (upper row) and WCSPH (lower row). From left to right: no kernel correction, classical Shepard correction, and our method. For both uncorrected and classical Shepard correction, we observe fine-grained noise in the density field. Using our technique, we achieve a completely smooth density field for WCSPH (lower right). Considering DFSPH, our method still significantly improves the smoothness of the density field.

Contact

Stefan Reinhardt
M. A.

Stefan Reinhardt

Doctoral Researcher

Patrizia Ambrisi
M.A.

Patrizia Ambrisi

Public Relations SFB 1313

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